I've never really thought about this before until I had our DLT drive sitting 
beside our desk during some renovations. What should the average DLT1 tape 
drive perform like during backup?
Ours happens to be a Lacie DLT1 (a Quantum DLT1 in a LaCie enclosure basically) 
which is used to backup approximately 120GB of data twice a week off of our two 
servers (~60GB each).  It is attached to one of the servers.

During a backup, or a flush, the tape drive writes data for 4 seconds, then 
rewinds for 1 second, then writes for 4 seconds, then rewinds for 1 second, etc.
This seems like a good way to wear out a drive.

I also have a DDS backup drive which backs up a number of Mac machines around 
the office using Retrospect.  This machine writes data in a single stream, and 
only ever seems to pause when it switches to the next machine, verifies data, 
or seeks specific data on a tape. 

Now this is a bit of a comparison of apples and oranges but should a DLT1 be 
able to write a near continuous backup stream rather than this apparent write 
4->seek 1, write 4->seek 1 cycle during backups and flushes?

Any suggestions on optimizing settings?
Here are my drive configs (minus stuff about logs, users, etc):

inparallel 4            
dumporder "BTBT"        
netusage  9600 Kbps     
dumpcycle 4 weeks       
runspercycle 20         
tapecycle 5 tapes    
dtimeout 1800           
ctimeout 30             
tapebufs 20
runtapes 1
tapedev "/dev/nst0"
rawtapedev "/dev/null"
holdingdisk hd1 {
    comment "main holding disk"
    directory "/var/amanda/dumps"       
    use -1 Gb           
    chunksize 0         
}
reserve 45

define tapetype DLT1 {
    comment "DLT1 tape drives"
    length 40960 mbytes         # 40 Gig tapes
    filemark 4000 kbytes        # I don't know what this means
    speed 2814 kbytes           # 3.5 Mb/s
}

define dumptype high-tar-comp {
   root-tar
   comment "partitions dumped with tar, compressed with gzip"
   priority high
   compress client best
   index yes
   exclude list "/etc/amanda/exclude.gtar"
}

define interface local {
    comment "a local disk"
    use 1000 kbps
}

define interface eth0 {
    comment "100 Mbps ethernet"
    use 1000 kbps
}




My disklist file:
blackhawk /clients / {
        high-tar-comp
        include "./clients"
        } 1
blackhawk /notclients / {
        high-tar-comp
        exclude "./clients" "./tmp"
        } 1